The present invention relates to a system for removing diaphragm halves from an upper shell of a turbine, moving the removed diaphragm halves to a location for refurbishing, and reinstalling the refurbished diaphragm halves into the upper shell.
Turbines, for example steam turbines, periodically require maintenance and generally include upper and lower shells which must be separated from one another along a horizontal midline for that purpose. As will be appreciated, each stage of a turbine includes an annular diaphragm split in half to provide upper and lower diaphragm halves in the upper and lower shells, respectively. The diaphragm halves in the upper shell are typically secured in the upper shell by bolt and key keeper arrangements located adjacent the midline horizontal joint along opposite sides of the turbine. Consequently, when maintenance is required, the upper turbine shell is unbolted from the lower shell and the upper shell, including the upper diaphragm halves secured therein, is lifted from the lower shell.
One heavy duty crane is generally employed to lift the upper shell and associated upper diaphragm halves from the lower shell. Using two cranes, the upper shell, including the diaphragm halves, is then inverted to enable the diaphragm halves to be lifted from the upper shell. Conventionally, this inversion process requires a lifting of the upper shell, a rotating of the shell 180° about a horizontal axis, followed by a lay-down of the upper shell on a stand. At many sites for turbines, bridge cranes are not available and two boom-type cranes are required for this lifting process. It will be appreciated that the requirement for two cranes substantially increases the cost of performing the maintenance as well as the outage time. It will also be appreciated that the weight of the upper turbine shell and associated diaphragm halves is substantial. For example, a typical turbine upper shell having thirteen upper diaphragm halves may weigh approximately 90,000 pounds with each upper diaphragm half weighing approximately 1,000 pounds. While a smaller crane may be used to lift the individual diaphragms from the inverted upper shell, it is still necessary to deploy two cranes, in the absence of a bridge crane, to remove and invert the upper shell. Consequently, there has arisen a need for a system for inspecting, maintaining and refurbishing the diaphragm halves of the upper shell of turbines at reduced costs and minimal outage time.